1. Field of the Invention
The present invention relates to a liquid discharge head that performs print recording, image formation, or the like on a recording medium by discharging liquid form discharge ports as liquid droplets.
2. Related Background Art
A liquid discharge apparatus (ink jet recording apparatus) is the apparatus of the so-called non-impact apparatus that performs print recording, image formation, or the like on various kinds of recording media by discharging liquid droplets with the supply of ink or the like to the liquid discharge head, while driving the piezoelectric element or the electrothermal converting element (heat-generating member) in accordance with the driving signals corresponding to recording information or image information, which is known as the excellent recording apparatus in that it performs a high speed printing with a lesser amount of noises with some other advantages, and widely adopted for use of the printer, word processor, facsimile apparatus, copying machine, and others that carry a recording mechanism.
The liquid discharge head used for a liquid discharge apparatus of the kind has the electrothermal converting element arranged in the liquid flow paths for the liquid discharge head that uses the electrothermal converting element, for example. With the provision of driving signals that serve as discharge signals for such element, thermal energy is given to liquid. Then, the bubbling pressure of each liquid droplet exerted at the time of bubbling (boiling) of liquid, which is generated by the phase changes of liquid at that time, is utilized for liquid discharges.
Also, for the liquid discharge head that uses the electrothermal converting method described above, there are two types: one is the edge shooter type where liquid droplets are discharged in parallel to the surface of the base plate having the electrothermal converting element (heat-generating member) arranged; and the other is the side shooter type where liquid droplets are discharged perpendicularly to the surface of the base plate having the electrothermal converting element arranged.
Now, hereunder, with the example of a liquid discharge head of side shooter type, the specific structure of the conventional liquid discharge head will be described in conjunction with FIG. 4 to FIG. 6.
FIG. 4 is a perspective view that schematically shows the conventional liquid discharge head of side shooter type, observed from above. FIG. 5 is a cross-sectional view that schematically shows the liquid discharge head arranged along the direction (5xe2x80x945 line) orthogonal to the arrangement direction of discharge ports represented in FIG. 4. Likewise, FIG. 6 is a partial cross-sectional view of the liquid discharge portion.
In FIG. 4 to FIG. 6, the element base plate 101 having the liquid discharge portion formed therefor is installed on the supporting member 120 through the holding member 121. On the surface side of the element base plate 101, there is arranged the flow path structural member 107 to form plural discharge ports 108 and liquid flow paths 111. Several tens or more of discharge ports 108 are provided for a actually finished product. Communicated with these discharge ports 108, the liquid flow paths 111 for supplying liquid are open almost in the same length as that of the discharge ports. Also, with the liquid flow paths 111, the liquid supply port 110 that supplies liquid from backside through the element base plate 101 and the liquid chamber 112, which is formed for the holding member 121, are communicated to arrange the structure in which the liquid chamber 112 receives the supply of liquid from outside.
As shown in FIG. 6, the heat-generating member (electrothermal converting element) 102 that gives heat to liquid for bubbling is provided for the element base plate 101 corresponding to each of the discharge ports 108. Also, the electrode wiring connected to each of the heat-generating member 102 is connected with the transistor circuit for driving the heat-generating member 102, respectively. For the transistor circuit, there have been known the method for incorporating such circuit on the element base plate 101 and the method for assembling the element incorporated in a separate member on the element base plate 101. Usually, for the element base plate 101 that has comparatively small numbers of heat-generating members 102 and discharge ports 108, it is generally practiced to adopt the method for incorporating the transistor circuit directly on the element base plate 101. However, in the case of the element base plate 101 that has comparatively large numbers of heat-generating members 102 and discharge ports 108 arranged for the purpose of widening the printing width, the structure that incorporates the transistor circuit on the element base plate tends to invite a significant reduction of production yield of element base plate. Therefore, the method for assembling the element incorporated on a separate member on the transistor circuit is considered advisable in terms of production yield. Here, the FIGS. 4 to 6 illustrate the example in which the transistor circuit incorporated on a separate driving element (driving IC) 113 is assembled on the element base plate.
FIG. 7 is a schematic view that shows the driving circuit of the kind for heat-generating member of the conventional ink jet recording apparatus. As described above, a plurality of heat-generating members 102 is provided, and one side of each wiring therefor is assembled by use of the block common wiring 301 on the VH power source side provided for each assembling (block) of the heat-generating members appropriately installed. Further, it is arranged to assemble each block common wiring 301 on the VH power source side by use of the head common wiring 302 on the VH power source. In this way, all the heat-generating members are electrically connected with the VH power source installed outside the recording head. The other wiring for heat-generating member 102 is connected with the driving transistor 1131 provided for the aforesaid driving IC 113 corresponding to each of the heat-generating members 102 one to one, respectively. The power supply line from the driving transistor 1131 is assembled by use of the block common wiring 303 on the GND side arranged per block, and assembled further by use of the head common wiring 304 on the GND side. In this way, all the heat-generating members are electrically connected with the electrodes of the VH power source and GND. Form the VH power source a constant voltage is supplied. The gate electrode of the driving transistor 1131 is connected with a driving control circuit (not shown), and with the appropriate control of the gate electrode, the heat-generating members 102 are driven arbitrarily to make an arbitrary image printing possible.
As shown in FIG. 6, the electrode wiring (not shown) connected with the heat-generating member 102 is connected to the thin-filmed electrode portion 103a, the common thick-filmed electrode portion 103b, and the IC assembling 104. Then, on the IC assembling 104, the driving IC 113 is assembled by the COB (chip on board) connection method using anisotropic conductive bonding film (ACF), solder bumps, or the like. Also, for the driving IC 113, the logic circuit and others are installed to drive transistor in addition to the transistor circuit for driving the heat-generating member 102. The logic circuit is connected with the flexible film (flexible wiring base plate) 114 through the electric connecting portion 104a formed at the edge of the element base plate 101. Further, the flexible film 114 is connected with the printed-circuit board (circuit base plate) 116, which is formed by a compound material of glass-epoxy and others. The printed-circuit board 116 has the electric connector 117 (FIG. 5) mounted in order to receive electric signals from outside. The flexible film 114 is folded substantially at right angle from the edge of the element base plate 101 along the side face of the supporting member 120, and the printed-circuit board 116 is fixed to the side face of the supporting member 120.
The thin-filmed electrode portion 103a connected with the heat-generating member 102, the common thick-filmed electrode portion 103b, the driving IC 113, and the electric connecting portion of the flexible film 114 are covered by a sealant 115, such as epoxy resin, excellent in sealing capability and ion insulation as shown in FIG. 6, because if the connecting portions are exposed, the electrodes and the base metal thereof are eroded by the adhesion of spreading liquid droplets from the discharge ports 108 and those bouncing off from the surface of a recording medium during print recording.
Now, when the driving IC 113, the common thick-filmed electrode 103b, the electric connecting portion of the flexible film 114, and others are sealed using a sealant 115 by the conventional art described above, it is generally practiced to adopt the method whereby to coat sealant 115 using a dispenser. This application of sealant aims at covering an object to be sealed completely so as to protect such portion sufficiently. However, in order to secure a sufficient protection and a sufficient sealing performance therefor, the coating area of the sealant should be arranged to be larger than that of the sealing object. As a result, there often encountered a problem that sealant spreads out from the sealing area, thus clogging the discharge ports 108. To counteract this, it is necessary to secure an area on the base plate for receiving the sealant that may spread out unavoidably. For the liquid discharge head, too, there is a need for the provision of such area to receive spread-out sealant (a margin prepared for receiving spread-out sealant) in order to perform sealing with a good production yield. Usually, it is required to provide a sufficient distance between the common thick-filmed electrode 103b and the driving IC. This ensues in a distinctive disadvantage in terms of efficiency needed for use of an expensive base plate. Also, in order to provide a smaller base plate, if the distance between the common thick-filmed electrode 103b and the driving IC is made smaller, while the coating amount and coating area of a sealant 115 are adjusted not to clog discharge ports 108, there often encountered a problem that the applied sealant 115 is not good enough to protect the common thick-filmed electrode 103b and the driving IC eventually.
Now, therefore, the present invention is designed to solve the problems of the conventional art as discussed above. It is an object of the invention to provide a liquid discharge head which is able to attain securing the sealing performance and effective utilization of the area of the head base plate simultaneously, and also, capable of implementing the cost down by increasing the obtainable numbers thereof per wafer with the smaller size of the head base plate by making the coating area of sealant for sealing the driving IC, electrode portions, and others smaller.
In order to achieve the object described above, the liquid discharge head of the present invention comprises discharge ports for discharging liquid, and a flow path structural member communicated with the discharge ports to constitute liquid flow paths for supplying liquid thereto formed on a base plate having discharge energy generating element for generating energy for discharging liquid, and electrode wiring formed by thin-filmed electrode and common thick-filmed electrode provided therefor. For this liquid discharge head, the flow path structural member covers the thick-filmed electrode.
It is preferable for the liquid discharge head of the invention to arrange the common thick-filmed electrode to be adjacent to the discharge ports, and also, to form the flow path structural member by photosensitive resin.
It is preferable for the liquid discharge head of the invention to arrange an IC assembling to be adjacent to the common thick-filmed electrode on the base plate, and while a driving IC is assembled on the IC assembling, the driving IC is sealed with sealant. In this case, the value of the distance between the common thick-filmed electrode and the driving IC should preferably be less than the value of thickness of the driving IC.
For the liquid discharge head of the invention, the discharge ports, common thick-filmed electrode, and driving IC are arranged in that order on the base plate, and the distance between the discharge ports and the common thick-filmed electrode should preferably be 5 mm or less.
It is preferable for the liquid discharge head of the invention to make the thickness of the common thick-filmed electrode 1 xcexcm or more.
It is preferable for the liquid discharge head of the invention to provide water repellent process for the surface of the flow path structural member near the circumference of the discharge ports, and also, provide water repelling process for the surface of the flow path structural member on the common thick-filmed electrode.
In accordance with the present invention, the liquid discharge head is provided with the flow path structural member that constitutes the liquid flow paths and discharge ports on the element base plate having discharge energy generating element arranged thereon, while the electrode wiring formed by thin-filmed electrode and common thick-filmed electrode, and the IC assembling are arranged on the element base plate thereof in order to apply driving signals to the discharge energy generating element, and then, the driving IC assembled on the IC assembling and electrode portion are sealed with sealant. For this liquid discharge head, the flow path structural member covers and seals the common thick-filmed electrode so that the width of the area corresponding to the common thick-filmed electrode is used as the area that receives the sealant that may spread out when it is applied to seal the driving IC. Further, the water repellent layer, which is formed near the circumference of discharge ports on the liquid discharge surface of the flow path structural member, is also formed on the area corresponding to the common thick-filmed electrode. In this way, it is made possible to reduce the amount of spread-out sealant sill more for the applied to the driving IC.
Thus, the sealing performance and the effective use of the base plate area can be attained simultaneously, to make it possible to downsize the element base plate of a liquid discharge head and increase the obtainable numbers thereof per wafer for the implementation of cost reduction.
Furthermore, with the area to receive spread-out sealant 15 on the flow path structural member 7, the step between the upper surface of the driving IC 13 and the area to receive spread-out sealant becomes smaller by the thickness portion of the flow path structural member 7. As a result, it becomes easier to control the spread-out amount of sealant. Thus, the driving IC 13 can be sealed with a lesser coating amount of sealant. With the lesser coating amount of sealant, the amount of swelling of sealant 15 on the driving IC can be made smaller, and the distance between the discharge ports 8 and a recording medium is made shorter accordingly for the enhancement of discharge precision.